A concrete pump is known having two separate piston-and-cylinder assemblies each comprising a cylinder, a pump subdividing same into a piston-side front compartment and a rod-side rear compartment, and a piston rod connected to the respective piston and extending out of the respective cylinder through the respective rod-side rear compartment. A liquid supply means having a high-pressure side and a low-pressure side can be connected via a reversing valve to these compartments to alternately operate them.
Such arrangements are normally divided into those of the piston-side pressurization type and the rod-side pressurization type. In the formar the reversing valve is connected to the front or piston-side compartments so as to presurize one while depressurizing the other, and vice versa, and the rod-side compartments are connected only to each other so that the liquid driven out of the one is taken into the other and vice versa. In the rod-side pressurization type the front or piston-side compartments are connected together and the reversing valve alternately pressurizes the rod-side or rear compartments.
Much time, energy, and speculation has been invested in determining which of these systems is best for which application. It appears that rod-size actuation is desirable in certain situations, and piston-side actuation in others. Nonetheless the user must opt for one system or the other when purchasing the machine. If a change is desired it is necessary to uncouple various hydraulic hoses, with concomitant loss of fluid, and recouple them in the appropriate manner, and then top off the reservoir to make up for the loss in fluid. Obviously such a procedure is onerous in the extreme, and leads owners of such concrete pumps often to use a type of actuation that is not suited to the job.